Non-railbound vehicle with an electric motor

ABSTRACT

A non-railbound vehicle with an electric motor in which the maximum output of the internal combustion engine will be available in its entirety for driving the vehicle without prejudice to convenience with respect to electrical actuation of accessory functions. The vehicle includes a drive control that provides a portion of the output generated by a generator for supplying power to the low-voltage vehicle power supply. The electronic drive control is programmed to provide a temporary interruption of the current supplied by the generator to the low-voltage vehicle power supply during operating phases in which the full output of the internal combustion engine is required for driving the vehicle. During these phases current is supplied to accessory electrical consumers via the vehicle battery.

BACKGROUND OF THE INVENTION

The invention is directed to a non-railbound vehicle having at least onedriving wheel coupled with an electric motor which is supplied withelectric current via output electronics which are influenced by anelectronic control. The current is generated by a generator that iscoupled to an internal combustion engine and functions at an operatingvoltage in the medium-voltage range. A low-voltage power supply is alsopresent for supplying power to the accessory electrical consumers of thevehicle, and includes a battery which is supplied with current obtainedby transforming a portion of the mechanical energy generated by theinternal combustion engine.

DESCRIPTION OF THE PRIOR ART

WO-A-9115378 discloses such an electrically driven vehicle as isdescribed above. In this vehicle a portion of the output generated bythe generator is supplied to the low-voltage power supply either by aseparate winding in the generator or from a DC-voltage intermediatecircuit via an inverter. A central control unit coordinates thedistribution of power to the driving motors, wherein antilock system andantiskid system functions can be realized. However, the central controlunit does not influence the supply of power to the low-voltage vehiclepower.

U.S. Pat. No. 5,166,584 discloses an electric vehicle in which the powerrequirement for high energy consumers is reduced when maximum output isrequired for powering the driving motors of the vehicle.

WO-A-9115378 discloses an electric vehicle with the features containedin the preamble of claim 1, in which a portion of the output generatedby the generator is supplied to the low-voltage power supply either bymeans of a separate winding in the generator or from the DC-voltageintermediate circuit via an inverter. A central control unit coordinatesthe distribution of power to the driving motors, wherein antilock systemand antiskid system functions can be realized. However, the centralcontrol unit does not influence the supply of power to the low-voltagevehicle power supply.

U.S. Pat. No. 5,166,584 discloses an electric vehicle in which the powerrequirement for high-energy consumers is reduced when maximum output isrequired for the driving motors.

A drive system for non-railbound vehicles which are outfitted with aninternal combustion engine whose output shaft is coupled with anelectric generator is known from the publication "Vehicletransmissions--present and future Getriebe in Fahrzeugen heute undmorgan!" (VDI-Berichte 878, 1991, pages 611-622). The driving wheels ofthe vehicle are connected with electric driving motors which draw theirdriving power from the generator. Because of the comparatively highoutput required to drive the vehicle, the generator operates in themedium-voltage range (e.g., 650 volts). A low-voltage power supply(e.g., 12 or 24 volts) in the form of a suitable vehicle power supplywith a vehicle battery is provided as is customary (also for safetyreasons) for the secondary or accessory electrical consumers found inthe vehicle such as interior and exterior illumination, ventilatormotors, windshield defroster, passenger compartment heating system,electric window openers, etc. In addition, a vehicle of this type canalso be outfitted with a storage for storing driving power, e.g., ashort-term storage in the form of a flywheel storage coupled with anelectric generator or a long-term storage in the form of an accumulator.

In conventional vehicles, the power supply for accessory electricalconsumers is generally provided for by a small electric generator, alsoknown as a dynamo, which is driven by the internal combustion engine.The dynamo also supplies the current required for charging the vehiclebattery which is then available for supplying current to the accessoryelectrical consumers when the dynamo supplies insufficient current (lowspeed, many consumers turned on) or none at all (internal combustionengine not in operation).

It has already been mentioned in the publication VDI-Bericht 878 thatthe generator producing the current for the electric driving motors cantake over the function of the dynamo. However, no further details aregiven.

In order to be able to power the low-voltage vehicle power supply fromthe generator, the medium voltage (over 60 volts) produced by thegenerator must first be stepped down to low voltage for the suppliedcurrent. This transformation presents no difficulties in an ACgenerator. This is also true for generators supplying a pulsed DCcurrent. Suitable electronic DC-DC converters are known for thispurpose.

The challenge faced by the future development of non-railbound vehicles,particularly with respect to drive technology, consists in appreciablyreducing the specific consumption values, that is, in ensuring the mosteffective possible use of the energy that is chemically combined in thefuel when converting this energy into driving power. In order to achievehigh efficiency in the internal combustion engine and to make thevehicle as lightweight as possible, the effort is made to build theinternal combustion engine so as to be as small as possible. In doingso, there is a tendency to reduce the output of the internal combustionengine. Therefore, in the future, maximum engine output will beperceptibly closer to the average required driving output than ispresently the case in conventional vehicles.

This development conflicts with another development toward increasedenergy consumption in the vehicle. The number of accessory electricalconsumers is constantly increasing, since an increasing number offunctions are realized electrically (e.g., sun roof, seat adjustment,mirror adjustment, air conditioning, etc.). This has already led to ahigher-output dynamo in conventional vehicles or even to simultaneousoperation of two dynamos. Not only does this result in the disadvantageof heavy units, but a relatively poor energy conversion efficiency mustalso be taken into account. For instance, in order to generate anelectrical output of 1.5 kW, a mechanical drive output in the order ofmagnitude of 3-5 kW is required, depending on speed. Thus, in aninternal combustion engine with 50 kW output, this already comprises upto 10% of the theoretically available drive output. However,particularly for reasons of safety (e.g., kickdown when passingvehicles), it is desirable to have as much as possible of the maximumoutput of the internal combustion engine available for driving thevehicle.

SUMMARY OF THE INVENTION

The object of the present invention is to modify a vehicle of thegeneric type at the lowest possible cost in such a way that its specificfuel consumption remains as low as possible and, when required, themaximum possible output of the internal combustion engine is fullyavailable for driving the vehicle without prejudice to convenience withrespect to the actuation of accessory electrical functions.

Pursuant to this object, and others which will become apparenthereafter, one aspect of the present invention resides in a non-railbound vehicle in which the electronic control provides a portion of theoutput generated by the generator for powering the low-voltage vehiclepower supply. Additionally, the electronic control is operative totemporarily interrupt the current feed from the generator to thelow-voltage vehicle power supply during operating phases in which thefull output of the internal combustion engine is required for drivingthe vehicle. During these phases the current is supplied to theaccessory electrical consumers by substituting in the vehicle battery.

The invention is applicable regardless of the type of device used as thegenerator (e.g., with permanent excitation or field excitation, with orwithout electronic commutation) or as the electric driving motor (e.g.,synchronous, asynchronous or DC motor). It provides, first, that theelectrical current required in the vehicle as driving power and for theaccessory consumers is generated only by the electric generator coupledwith the driven shaft of the internal combustion engine, that is, noseparate dynamo is used. This not only economizes on weight in anadvantageous manner, but is also advantageous in that the generator isenabled to generate current at an appreciably higher efficiency than waspreviously conventional in dynamos. The use of a so-called "generatorstep-up drive" as is sometimes needed to achieve sufficiently highspeeds in the dynamo at low internal combustion engine speeds isdispensed with entirely. All of this contributes to maintaining a lowspecific fuel consumption of the vehicle. Additionally, the costsrequired for this purpose are small. Essentially, only a voltagetransformer is required for transforming the current required for theaccessory electrical consumers and for charging the vehicle battery fromthe originally generated medium voltage (preferably around 60 to 1500volts, in particular in the range of 650 volts) to the low voltage ofthe vehicle power supply (e.g., 12 or 24 volts).

A particularly important feature of the invention consists in that theelectronic control which is already present in the vehicle and whichinfluences the operation of the internal combustion engine, generatorand electric motors for the vehicle drive depending on the drivingoutput demanded by the driver is expanded in such a way that a circuitis activated in operating phases in which the power requirement isparticularly high (e.g., kickdown), that is, at or near the theoreticalmaximum output, which circuit temporarily interrupts the currentsupplied by the generator in the low-voltage vehicle power supply andensures the supply of current to the accessory electrical consumers fromthe vehicle battery by way of substitution. In such phases, which areonly of short duration as a rule, the maximum possible output of theinternal combustion engine is fully available for driving the vehiclewithout prejudicing convenience by switching off individual accessoryconsumers. Of course, the importance of the additional available outputincreases the lower the output at which the internal combustion engineis designed. These output reserves are mobilized to a great extent viasoftware, that is, without large cost. Only a circuit which temporarilydisconnects the low-voltage vehicle power supply from the generatorpower is required. When the maximum output requirement phase is at anend, the electronic control can again release the supply of power fromthe generator so that the vehicle battery can also be charged once more.

The generator can power the low-voltage vehicle power supply directly(via the voltage transformer). In a particularly advantageous manner,the invention can be constructed in such a way that the voltagetransformer for powering the low-voltage vehicle power supply drawscurrent from an intermediate circuit, in particular a DC-voltageintermediate circuit, which is arranged downstream of the generator, thecurrent for the electric driving motors also being drawn from thisintermediate circuit.

Since the necessary components for carrying out the invention are in aworking connection with the rest of the system via electric lines, theymay be freely accommodated in the vehicle. Thus, not only is it possibleto economize on weight, but the weight distribution and utilization ofspace can also be optimized.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a block diagram of a drive train of a non-railbound vehiclepursuant to a first embodiment of the invention; and

FIG. 2 is a block diagram similar to FIG. 1 of a second embodiment ofthe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, an internal combustion engine 1 is coupled via its crankshaftwith a generator 2 which is constructed, for example, as a permanentlyexcited DC generator with electronic commutation. The generator 2produces alternating voltage which is fed to a DC-voltage intermediatecircuit 4 after rectification in a rectifier 3. The driving power foroperating the electric motors 8 which are, for instance, coupled with awheel 9 of a vehicle (not shown) is drawn from the DC-voltageintermediate circuit 4. Like the generator 2, the electric motors 8 arepreferably constructed as permanently excited DC generators withelectronic commutation. The electric current is supplied to the electricmotors 8, e.g., as alternating current (block 7). The electronic controlthat controls the generator 2 is designated by GST, while the electroniccontrols of the electric motors 8 are designated by MST, although onlyone of the latter is shown by way of example. An overriding drivecontrol FST is superimposed on the controls for the electric motors 8and generator 2. A driver selects the desired output by way of aconventional accelerator 15. The signal flow is shown in dashed lines todistinguish it from the power flow. The operating voltage in theDC-voltage intermediate circuit 4 lies in the medium-voltage range,preferably at approximately 650 volts. In addition to the electricmotors 8, accessory electrical consumers 10 (e.g., ventilators,windshield defroster, etc.) in the vehicle must also be supplied withcurrent. For this purpose, a low-voltage vehicle power supply, e.g., 12or 24 volts, containing a vehicle battery 6 is provided. In order tocharge the battery 6 and/or to power the accessory consumers 10 innormal driving operation the required current is removed from theDC-voltage intermediate circuit 4. Since the voltage level of theDC-voltage intermediate circuit 4 is essentially too high, the voltageis stepped down to the range of the vehicle power supply voltage in anelectronic transformer 5. In operating phases in which the highestpossible output should be available for driving the vehicle, theelectronic control FST temporarily interrupts the connection between theDC-voltage intermediate circuit 4 and the voltage transformer 5 by meansof a switching device (interrupter 11) so that all of the currentgenerated by the generator 2 can be supplied to the electric motors 8.During these phases, the accessory consumers 10 are supplieduninterruptedly via the vehicle battery 6. When high output is no longerrequired (e.g., upon completion of a passing maneuver), the connectionbetween the DC-voltage intermediate circuit 4 and the voltagetransformer 5 is restored by the electronic control FST so that thebattery 6 can be charged again and/or the accessory consumers 10 can besupplied directly from the DC-voltage intermediate circuit 4.

Of course, rather than drawing current from the DC-voltage intermediatecircuit 4, it is also possible to branch off the current for theaccessory consumers 10 from the generator 2 as is shown in FIG. 2. Avoltage transformer 12 is provided for transforming the voltage to thelevel of the low-voltage vehicle power supply by stepping down andrectifying the alternating voltage of the generator 2. The voltagetransformer 5 shown in FIG. 1 is dispensed with in this case. In otherrespects, the operation of the construction according to FIG. 2 conformsto that shown in FIG. 1 and need not be discussed again.

The generator 2 may also be outfitted with a suitable special device(e.g., a special low-voltage winding or circuit) for supplying powerdirectly to the low-voltage vehicle power supply, thus dispensing with astepping down of voltage (blocks 5 and 12). When increased drivingoutput is required, the drive control FST interrupts the power supply tothe low-voltage vehicle power supply in this case also.

The principle according to the invention can also be readily appliedwhen using AC generators and AC motors. Of course, rectification mustthen be effected before feeding to the vehicle power supply. Theadvantages achieved in making available the maximum output of theinternal combustion engine as driving power without loss of conveniencein dispensing with a separate dynamo are still retained.

We claim:
 1. A series hybrid vehicle, comprising:at least one drivingwheel; an electric motor drivingly coupled to the at least one drivingwheel; means for supplying electric current to the electric motor;electronic control means for influencing the electric current supplymeans; an internal combustion engine coupled to the electric motor bythe electronic control means; a generator operatively coupled to theinternal combustion engine for generating the electric current as anoutput with an operating voltage in a medium-voltage range; accessoryelectric consumers; and vehicle power supply means operative in alow-voltage range for supplying power to the accessory electricconsumers, the vehicle power supply means including a battery, theelectronic control means including a drive controller which is operativeto direct a portion of the generator current output to the vehicle powersupply means and is further operative to temporarily interrupt thecurrent fed to the vehicle power supply means when full output of theinternal combustion engine and generator is needed to drive the vehicleand temporarily connect the accessory electrical consumers to thebattery.
 2. A vehicle as defined in claim 1, and further comprising anaccelerator operatively connected to the electronic control means so asto permit actuation of the electronic control means by a driver of thevehicle.
 3. A vehicle as defined in claim 1, wherein the generator isoperative to generate an electric current with an operating voltage in arange of above 100 volts to 1500 volts.
 4. A vehicle as defined in claim1, wherein the vehicle power supply means is operative in a range below60 volts.
 5. A vehicle as defined in claim 1, and further comprisinginterruption means operatively connected to the drive controller fortemporarily interrupting the current feed from the generator to thelow-voltage vehicle power supply means.
 6. A vehicle as defined in claim5, and further comprising voltage transformer means for reducing thecurrent supply for the low-voltage vehicle power supply from themedium-voltage range of the generator to the voltage of the low-voltagevehicle power supply means, the voltage transformer means beingconnected directly to the generator via the interrupter means.
 7. Avehicle as defined in claim 1, and further comprising voltagetransformer means for reducing the current directed to the low-voltagevehicle power supply means from the medium-voltage range of thegenerator to the voltage of the low-voltage power supply means.
 8. Avehicle as defined in claim 7, and further comprising a rectifieroperatively arranged down stream of the generator for generating directcurrent, and a DC-voltage intermediate circuit operatively connecteddown stream of the rectifier to supply the electric motor with currentfor driving the vehicle, the voltage transformer means including a DC-DCconverter connected to the DC-voltage intermediate circuit.
 9. A vehicleas defined in claim 8, wherein the DC-voltage intermediate circuit israted at an operating voltage in a range of 60 to 1500 volts.
 10. Avehicle as defined in claim 9, wherein the DC-voltage intermediatecircuit is rated at an operating voltage of approximately 650 volts. 11.A vehicle as defined in claim 1, wherein the generator includes meansfor supplying power directly to the low-voltage vehicle power supplymeans.
 12. A vehicle as defined in claim 11, wherein the means forsupplying power directly to the low-voltage power supply means includesa low-voltage winding.